Dr.Neo:
Did you find out why Mario Kart 64 and Wave Race 64 Japanese and US but NOT Pal can not keep save games?
After you saved the game, the save game disappears after about one minute when you remove the N64 Myth card from the N64.
Other games like Super Mario 64 Japanese 1.0 for example which uses also 4KBit EEPRom works fine, just finished the game with 120 stars after about 1 week of playing. Goldeneye 64 Japanese also works fine.